X9 on first flight a lot problems

Hello guys, i have a few problems, 1st is when i first time takeoff did everything from beggining, like it said, and got huge oscilations, i don’t know what to do else, i changed frame, gps, pixhawk, kinda everything was changed and still same problem. it doesnt even hold the altitute, it just accelerating by him self on vertical position, and release that acceleration, if someone could help me i would be really greatful. Thanks for your time.

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Tell us a bit more about the copter: props, motors, ESCs, Battery details, take off weight

EDIT: sorry, I see X9’s are 3411 props with inbuilt ESCs of course.
You need to set:


That thrust expo is a little lower than in the Initial Parameters calculator - we’ll get to that later, but use this new value for now.
I’ll keep checking the log for more.

There is a lot of X axis vibration that you will need to fix. It could be a problem with the frame itself, something loose, or the flight controller mounting or wiring.

You will probably need to add some dummy payload to this copter since it is quite overpowered. Make sure the dummy payload is very secure and wont shift or vibrate.

Your current sensor is not working, but voltage is. If the current cant be measured then set
otherwise it would be nice to have the current measurements, but not as essential as voltage.
All the battery voltage related settings and the Fence are all essential on these big copters - dont skip over any of the settings I specify.

Let us know exactly what battery you have. The settings I provide here will be OK now and we can refine them later if we have to.

Set these ready for the next test flight.

GPS_GNSS_MODE,5     // or 65 , whichever works best
INS_HNTCH_ENABLE,1  // write this then refresh params to see the rest

Try a takeoff in Stabilise mode - if there are oscillations land immediately and reduce these
If you get airborne OK use AltHold mode as much as possible, just do some gentle pitch and roll movements, nothing special.
Let’s see that .bin log next.

You are near some areas with GPS interference, so just be aware. With FENCE_ENABLE,1 it could take quite some time for Home to be set before you can arm. This is the safest option for these big copters.
I would not advise disabling the fence, or when it’s most needed your copter will head of to Sea of Japan or somewhere less desirable.

Areas without green/yellow/red maybe have signal but no suitable flights to record data - example: no fly zone.

hello, i put your settings, and this is the look what i get : we still have vibrations, but it holds altitude better, no such a high swings up and down. i dropping file for you, and waiting for response. It’s weight with batteries is 19kg, I don’t think that’s a weight problem, for the frame, it’s not a first one, what i build, others working well, but this one, is challange. batteries are TATTU 30000 mAh, 25c.

Yes X axis vibrations are still very high.
Vibrations are a physical problem you have to fix - no amount of parameter changes will get rid of them.
Being just X axis, and almost no Y component, it is probably NOT prop balance, and more to do with how the flight controller is mounted, or some other part vibrating - like a GPS mast or cable.
A couple of photos could help us narrow that down.

Adjust these:


But dont fly until there is some positive action taken to fix the vibrations - it is really affecting pitch PIDs badly. Since flight is possible I’d like to see how it is without so much vibrations before we change the PIDs too much.
Definitely consider adding some dummy payload, the throttle is so low that stability and tuning will be tricky.
After takeoff in Stabilise, use some AltHold mode for a while, the altitude should really get more steady after a few seconds.

@xfacta Hello again, thanks for your time, i sending you photos, nothing touching computer, still have that vibration, what else i could do ?


@xfacta well, i put some weight on it. +4 kg, and now no vibration… :smiley: didn’t expect that, but yeah, no vibrations, some oscilations but little bit. And I want to ask, how to configure notch filter, and wondering, to what you need to look, to configure it great. Thanks for everything :slight_smile:

I couldnt access those photos, must have an access restriction.

If vibrations are fixed and everything checks out OK you could probably just do Autotune - but please pass on another log before you do. Remember to do more AltHold, if flight is very stable use Loiter

We have your harmonic notch filter working OK now, it will track throttle, although we will need to see more logs.
Harmonic Notch Filter was configured this way:

  • you already had the batch logging set
  • I used the Filter Review Tool to check the required values
  • we just need to recheck it as flight improves to ensure the HNOTCH works in all situations


well i did more some fight’s, with weights, it’s pulsing, upand down, vibration started again, evewn with weight, and no wires touching it, sorry for late response, it’s bounching up and down, weight doesn’t helping, It’s like putting throttle and releasing and that in some mini interval like 0.1s It’s pulsing. I even put extra pipes near motors to push each other, motors stopped vibrating, but same bad vertical acceleration. here is the file…

https://fastupload.io/NCGgGTBrlnRx43K/file < here is photos,should be okay now.

You must have reset to defaults or something - all the parameters and values we set are gone.
Work through the previous posts and put back everything we had in place.

Then use AltHold for flight ! It needs this to learn the hover throttle and it will tell us more about what is going on.

Over the years people have NOT had good experiences with aluminium frames.
Those arms could be OK, but the alloy base plates wont be helping. Aluminium is too soft and it seems to promote vibration.
On small quads aluminium arms can be OK provided the base plates are something else - almost anything else except aluminium.

Okay, i wish i could put alt hold, but it’s oscilting too much, even with your params. So thats why i decide to put back initial tuning params. Aluminum isnt’t a problem, i have some monsters with aluminum, hexa x11 x9 max. I had kinda same issue with x8 yesterday, vibration was in Y axis, so both didn’t worked, but i just rewrite older program, 4.4.3 and now it’s working perfectly. yesterday i couldn’t even takeoff on stabilize. Today all fine. About x9, so the problem is, i first time have that issue like I have it now, and wondering what could be wrong

@xfacta Hello, I had problem, problem is crash. What could happend. without payload was kinda okay, but we saw compass inconsistency, when it on ground, it turning by him self around 20 degrees, when it takeoff to air, it turning to that side, where it turned on ground. When I put payload, it could held one spot, started to do egg, and did it till crash, I couldn’t even control it. We thinking, it causing by electric field, because, pixhawk isn’t far from cables, and there is goin a lot of power in those cables, and somehow can create magnetic field, and it hurts compass.

Here is file : https://fastupload.io/nrVnt38LDlU6pV3/file

Had you done a in flight magfit?

Yes already 30 times done

Then move the sensors away from the high current cables. And what kind of vibe levels do you have?

Vibe on Y axis is really high, 25-40 sometimes even more. Other two is kinda fine.

But that vibration what i mention above, stepping in just when something happends with compass. Because when it’s just hover. All fine low vibrations. When it starting to do something like egg, then vibrations starting to raise

That means that something is not optimal. Fix the vibrations before trying to fix anything else.

@amilcarlucas @xfacta Hello guys, sorry for late response, I have fixed vibrations, and without weight, vibrations about 2-7, so i decide to put some weight, dummy payload, 11,5 kg. And guess what is going on, i have huge vibrations, almost 90 on takeoff and when standing still it’s ~30-60. What it could be and where i could look to fix that thing ? Y axis most vibrations, other have ~30 with payload.

My files - UploadNow.io Here is the file @amilcarlucas @xfacta